How the Deepwater Spill Could Affect Hurricane Development

by: Michael Ferrari

As we have just entered the 2010 Tropical Atlantic Hurricane Season, many questions are circulating that address the possibility of the BP Deepwater Oil leak affecting the development of storms in the Gulf of Mexico. Tough to address this one with a definitive answer – despite what many in the media are saying in an effort to draw comparisons, a release like this is pretty new territory, so there are no true analogs to use. From a physical standpoint, there are plausible scenarios that could support enhancement or suppression:

Arguments for more activity (as a result of the spill):

  • The sheen at the surface will absorbing more solar radiation, in the process increasing water temperature and leading towards a higher probability of formation over warm waters.
  • The sheen is not one contiguous mass, so there will still be plenty of opportunity for an active pattern to emerge.

Arguments for less activity (as a result of the spill):

  • The sheen will be thick enough at the surface to prevent evaporative convection, thereby reducing fuel for storms to form/strengthen.
  • Thin streams of oil associated with the sheen can break or disrupt a system moving across the Gulf.

Regarding the actual oil slick at the surface, there are actually two types of slicks which are forming. The first is a thinner sheen (< 10mm), which is lighter in color, and therefore absorbs less radiation (actually reflecting) and not necessarily contributing to an additional warming of the surface waters. The second is a thicker mass (10mm to 100mm+ ) which is darker, absorbing more solar radiation; this would serve to heat the surface water. However, despite warmer waters, a thicker sheen can also serve to suppress evaporation so this would be a storm inhibitor. There is also the possibility that the first/second major storm moving into the Gulf will disperse enough oil so that it will not have a significant measurable effect on the development of subsequent storms. In a year like this year where everyone is calling for higher seasonal numbers, it might not really matter much when we look back to summarize the season at the end of the year. Such a scenario would have more serious environmental effects, as the oil would be transported to a much larger area, potentially affecting coastal ecosystems, but this is a separate issue. Rather than the oil affecting hurricanes, more appropriate view is actually the converse: hurricanes will likely affect the distribution of the oil.

As of now, I would have to lean towards the spill not significantly affecting tropical system development or movement in the Gulf of Mexico during the 2010 hurricane season. Despite the areal extent of the spill, most medium sized hurricanes are far larger in size. And the fact that the sheen is very fragmented (ie., not one large oil slick covering a huge area) even weakens the argument that it will affect any tropical development. Weather Trends, like many of the other public and private forecasting groups, has called for a very active season, with more development skewed towards the Aug/Sept/Oct period. At this point, we see no reason to change our projected numbers as a result of this activity.

For an overview of the Weather Trends seasonal outlook, please click here.

[Ed. note: This information should be of particular interest to investors in property insurers and reinsurers, such as ALL, CB, TRV, RGA, OTC:SWCEY, PRE, RE.]

Disclosure: none